A magnetostrictive guided wave sensor suitable for high-pressure / fluid-filled environments

Abstract

This invention relates to a magnetostrictive guided wave sensor suitable for high-pressure / fluid-filled environments. The sensor comprises a tile-shaped permanent magnet, a detection coil, magnetostrictive patches, a magnetic yoke, hose clamps, an elastic layer, and a sleeve. The elastic layer wraps around the pipeline. Two arc-shaped magnetostrictive patches are symmetrically attached to the outside of the elastic layer. A circular hose clamp is fitted at each edge of the outer end of the magnetostrictive patch. A detection coil is wound around the outer surface of the magnetostrictive patch between the hose clamps. The detection coil is covered by a sleeve. Four evenly distributed fan-shaped slots on the sleeve each contain a tile-shaped permanent magnet. A strip-shaped magnetic yoke is fixed to each of the radial sides of each tile-shaped permanent magnet. The sensor obtained by this invention has higher transduction efficiency, and the novel guided wave sensor is suitable for monitoring pipeline defects in high-pressure fluid-filled environments.

Description

Technical Field

[0001] This invention applies magnetostrictive Fe-Co materials to the field of guided wave sensors, primarily involving a novel magnetostrictive guided wave sensor based on Fe-Co materials. This sensor can be applied to high-pressure liquid-filled pipelines to measure the location of pipeline defects in high-pressure liquid-filled environments. The core components of this guided wave sensor are a high magnetostriction coefficient magnetostrictive material patch, a tile-shaped permanent magnet, a detection coil, a hose clamp, an elastic layer, a magnetic yoke, and a sleeve. Its advantages include high guided wave excitation efficiency and low signal attenuation, enabling its application in high-pressure liquid-filled pipelines and overcoming the phenomenon of defect undetectability due to guided wave amplitude attenuation in liquid-filled pipelines. Background Technology

[0002] Magnetostrictive guided wave sensors utilize the magnetostrictive effect of magnetostrictive materials to realize guided wave sensors, primarily used for pipeline defect detection and health monitoring. Southwest Research Laboratories in the US and TWI Research Laboratories in the UK, after more than twenty years of technological accumulation and research, have respectively developed the MsS guided wave detection instrument and the Teletest long-distance guided wave detection instrument. As typical commercial guided wave detection instruments, they have been widely applied in various industries and have achieved good results. Due to the advantages of this sensor, such as non-contact operation, high sensitivity, good linearity, single-point excitation, long-distance monitoring, and adaptability to harsh environments, it has been widely used in pipeline defect detection and pipeline structural health monitoring. Pipelines, as one of the five major modes of transportation, have unique advantages compared to traditional transportation methods such as railways, highways, and waterways, including lower initial investment, lower transportation costs, higher safety, and environmental friendliness. They are particularly suitable for long-distance transmission of flammable and explosive oil and natural gas. Currently, magnetostrictive guided wave sensors use Fe-Co magnetostrictive materials as patches. This alloy was chosen for three reasons: first, it exhibits the Widmann effect; second, it has good plasticity and is easily processed into thin sheets; and third, it has a high magnetostriction coefficient, ensuring the stability of the propagation velocity of torsional waves in high-pressure liquid-filled environments and overcoming the problem of guided wave signal attenuation in liquid-filled environments. Professor Liu Zenghua constructed a complete guided wave detection device based on the magnetostrictive principle using integrated devices. Based on this device, he used the T(0,1) mode with an excitation frequency of 50kHz to detect long water-filled and unfilled pipelines. The results show that torsional guided waves in this mode can perform non-destructive testing on water-filled pipelines. The viscosity and density of the liquid in the liquid-filled pipeline limit the application range of magnetostrictive guided wave sensors. However, with the increasing length of pipelines transporting natural gas and oil, there is an urgent need for guided wave sensors that can operate stably under high-pressure environments while maintaining a certain transduction efficiency. For sensors to operate in liquid-filled environments, magnetostrictive materials with high magnetostriction coefficients must be used as patches. The applicant has conducted systematic research on magnetostrictive patches, optimizing alloy composition and processing techniques to prepare Fe-Co magnetostrictive alloy patches (Φ=0.15mm). These alloy patches have a magnetostriction coefficient exceeding 90PPM, meeting the operating conditions of guided wave sensors in high-pressure liquid-filled environments. Simultaneously, custom-designed neodymium iron boron tile-shaped permanent magnets with strong magnetic fields are used. Furthermore, current magnetostrictive guided wave sensors use epoxy resin to couple the sensor to the pipe, making it difficult to change the relative position after installation, hindering reuse, and causing difficulties in subsequent pipe cleaning. Therefore, using a clamp to couple the sensor to the pipe allows for changing the sensor's installation position and enabling unidirectional excitation of guided waves at different frequencies. However, in high-pressure liquid-filled environments, while the sound velocity changes little under different pressures, the echo signal amplitude attenuates significantly, rendering existing guided wave sensors unsuitable.Therefore, in order for the sensor to identify the specific location of pipeline defects under high pressure, it is necessary to redesign the sensor structure to be suitable for working in a high-pressure liquid-filled environment, add echo amplitude compensation function, and reduce or even eliminate the impact of pressure changes on defect identification.

[0003] Kim's team (10.1109 / TUFFC.2010 / 1535) proposed a magnetostrictive patch sensor for exciting torsional guided waves. It uses a rectangular permanent magnet with a rectangular circumferential magnetization to provide a circumferential static magnetic field for the magnetostrictive patch. However, it did not take into account the optimal excitation magnetic field of the magnetostrictive material, and the magnetic field generated by the rectangular magnet had poor uniformity, resulting in the excited guided wave signal containing many different modes. Summary of the Invention

[0004] The purpose of this invention is to address the shortcomings of current technologies by providing a magnetostrictive guided wave sensor suitable for high-pressure / fluid-filled environments. This sensor employs four sets of circumferentially magnetized tile-shaped permanent magnets, with triangular magnetic yokes installed at both ends of each set of permanent magnets to guide the magnetic field into the magnetostrictive patch, thereby improving the excitation and reception efficiency of the guided wave. Using Fe-Co magnetostrictive material as the magnetostrictive patch, and employing a detection coil to generate an alternating magnetic field or induced voltage signal, the magnetostrictive guided wave sensor is obtained. This invention applies this magnetostrictive guided wave sensor as both a guided wave excitation sensor and a guided wave receiving sensor in pipeline defect detection devices, exhibiting higher transduction efficiency and suitability for monitoring pipeline defects in high-pressure fluid-filled environments.

[0005] The technical solution of this invention is:

[0006] A magnetostrictive guided wave sensor suitable for high-pressure / fluid-filled environments includes a tile-shaped permanent magnet, a detection coil, a magnetostrictive patch, a magnetic yoke, a hose clamp, an elastic layer, and a sleeve.

[0007] The positional relationship is as follows: the elastic layer is wrapped around the pipeline, and two arc-shaped magnetostrictive patches are symmetrically pasted on the outside of the elastic layer. The distance between the two patches is 2-3 mm, and the radial end of the patch is the same length as the radial end of the elastic layer. A circular hose clamp is fitted at the edge of each end of the magnetostrictive patch. A detection coil is wound on the outer surface of the magnetostrictive patch between the hose clamps. The elastic layer, the magnetostrictive patch and the detection coil form a hollow cylinder. The hollow cylinder is covered by a sleeve. In each of the four evenly distributed fan-shaped slots on the sleeve, there is a tile-shaped permanent magnet. On each radial side of each tile-shaped permanent magnet, there is a strip-shaped magnetic yoke.

[0008] The elastic layer is a closed or open cylindrical body; when it is an open cylindrical body, it has a radially oriented through groove with a width of 0.5 to 1.0 cm; the material is polyurethane.

[0009] The sleeve is made of thermoplastic plastic, and has four sector-shaped grooves inside. The radial length of the sleeve is the same as that of the permanent magnet.

[0010] The aforementioned tile-shaped permanent magnet is made of neodymium iron boron.

[0011] The detection coil is made of enameled wire, wound into a hollow cylinder, with 50 to 200 turns;

[0012] The magnetostrictive patch is rectangular in shape, located between the elastic layer and the coil, and is made of Fe-Co alloy.

[0013] The magnetic yoke is made of silicon steel, has a radial strip shape, a right-angled triangular cross-section, a height less than or equal to the thickness of the magnetic tile, and a radial length the same as the patch and the permanent magnet.

[0014] The hose clamp is made of stainless steel.

[0015] A defect detection device for pipelines in liquid-filled / high-pressure environments includes: a PC, a signal generator, a power amplifier, a voltage preamplifier, an oscilloscope, a pressurizing pump, an excitation sensor, and a receiving sensor. The PC is connected to both the signal generator and the oscilloscope. The signal generator is connected to the excitation sensor via the power amplifier. The oscilloscope is connected to the receiving sensor via the voltage preamplifier. The excitation sensor and the receiving sensor are respectively fitted onto the pipeline to be tested.

[0016] The excitation sensor and the receiving sensor have the same structure and are both magnetostrictive guided wave sensors. The number of turns of the detection coil in the receiving sensor is greater than or equal to the number of turns of the detection coil in the excitation sensor.

[0017] A method for detecting defects in pipelines in liquid-filled / high-pressure environments includes the following steps:

[0018] (1) Install the excitation sensor and the receiving sensor at one end of the pipeline respectively;

[0019] (2) Output the Hanning window modulated sine pulse waveform to the signal generator via the PC terminal;

[0020] (3) The signal generator produces a pulse wave which is input to the power amplifier;

[0021] (4) The power amplifier inputs the signal to the detection coil of the excitation sensor;

[0022] When the detection coil receives a pulse signal, it generates an axial alternating magnetic field, which interacts with the circumferential static magnetic field generated by the permanent magnet. According to the magnetostrictive effect, a torsional guided wave is generated in the magnetostrictive patch. The guided wave is transmitted from the patch to the pipe and propagates radially in the pipe wall and liquid.

[0023] If there are no defects inside the pipe, the received signal will not contain wave packets of the corresponding defect reflection signal.

[0024] If a defect or end is encountered during propagation and reflection occurs, the reflected signal will change the magnetization state of the magnetostrictive patch when it reaches the receiving sensor. According to the inverse magnetostrictive effect, the detection coil will induce a voltage signal, and then proceed to the next step.

[0025] (5) The voltage signal detected by the sensor's detection coil is input to the voltage preamplifier;

[0026] (6) The signal is amplified and filtered by a voltage amplifier before being input to the oscilloscope;

[0027] (7) The signal is averaged by an oscilloscope and then input to the PC.

[0028] (8) After the PC performs wavelet transformation and other processing on the signal, the specific location of the pipeline defect is finally determined by the position of the defect echo in the detection signal and the propagation speed of the torsional wave.

[0029] The pressure environment of the pipeline is 0-8 MPa.

[0030] The liquid is water, glycerin, or petroleum.

[0031] The method for detecting defects in pipelines in liquid-filled / high-pressure environments is characterized in that the defects are pipeline corrosion pits, pipeline cracks, or weld seams.

[0032] The essential features of this invention are:

[0033] When the guided wave sensor operates, the signal generator produces a Hanning window modulated sinusoidal pulse voltage applied to both ends of the excitation sensor. This pulse generates an axial alternating magnetic field, which superimposes with the circumferential static magnetic field generated by the tile-shaped permanent magnet to form a spiral magnetic field. Based on the magnetostrictive effect, the magnetostrictive patch deforms instantaneously and generates a torsional wave, which propagates towards both ends of the pipe at a certain speed. When the torsional wave encounters the pipe end or a pipe defect, it is reflected. The reflected torsional wave propagates to the receiving sensor, changing the magnetization state of the magnetostrictive patch. Based on the inverse magnetostrictive effect, the receiving sensor induces a voltage signal. The time interval between receiving the defect reflection signal and generating the driving pulse, multiplied by the speed of sound of the torsional wave, gives the current location of the pipe defect. The pipe liquid pressure is controlled by a pressurization pump, and the pressure is measured and corrected in real time. The amplitude of the echo signal within the pressure variation range is measured. To ensure constant pressure measurement under high pressure, stainless steel end caps are installed at both ends of the pipe to maintain a constant internal pressure. Based on the above improvements, and after extensive experiments and optimization of the configuration of each part, a magnetostrictive guided wave sensor for high-pressure conditions was designed. Experiments yielded various design parameters that ensured the guided wave sensor could accurately measure under any pressure environment below 8 MPa and optimize the detection signal.

[0034] The beneficial effects of this invention are as follows:

[0035] Current magnetostrictive guided wave sensors suffer from significant signal amplitude attenuation, numerous interference modes, and difficulty in identifying defect locations due to limitations in the strength and uniformity of the static magnetic field generated by their static magnetic structures. Consequently, these sensors fail when the liquid pressure is too high. However, the new static magnetic structure, with its higher transduction efficiency, allows the new guided wave sensor to be used in liquid-filled environments below 8 MPa.

[0036] Specifically, this is reflected in:

[0037] 1. Utilizing the magnetostrictive effect and inverse magnetostrictive effect of Fe-Co sheet material, the location of pipeline defects is converted into a time-dependent voltage signal, enabling precise measurement of the defect location. The magnetostrictive patch uses Fe-Co, a novel magnetostrictive material with a high Curie temperature and a magnetostriction coefficient of not less than 90 PPM. The permanent magnet uses a tile-shaped permanent magnet, generating an optimal bias magnetic field suitable for Fe-Co with high uniformity, thus improving the transduction efficiency of the magnetostrictive guided wave sensor.

[0038] 2. To ensure the torsional wave is excited under the optimal bias magnetic field, the dimensions and lift-off distance of the permanent magnet were calculated in the simulation software. To optimize the magnetic field distribution, triangular strip yokes were added to both ends of the permanent magnet to guide the magnetic field onto the magnetostrictive patch. Four sets of tile-shaped permanent magnets were symmetrically distributed with the same polarity at adjacent ends, generating a static magnetic field of approximately 27 kA / m. Semi-circular end caps were added to both ends of the pipe, with a pressure pump connected to the right end to maintain a constant pressure in the pipe. The zero-crossing time displayed on the detected voltage waveform can represent the propagation time of the torsional wave generated at the excitation end.

[0039] 3. Based on the above improvements, and after extensive experimentation and optimization of the configuration of each component, a magnetostrictive guided wave sensor for high-pressure liquid filling conditions was designed. Experiments showed that the excitation sensor was wound with 100 turns of coil, and the receiving sensor with 150 turns of coil. The excitation pulse signal was 100V amplitude, 45kHz frequency, and 5-cycle period, modulated with a Hanning window sinusoidal pulse wave. The receiving sensor received the maximum detection voltage. The magnetostriction coefficient of Fe-Co material was measured to reach 98×10⁻⁶ under the optimal bias magnetic field of 25-30kA / m. -6 The PPM, a tile-shaped permanent magnet, generates a bias magnetic field strength of 27.4 kA / m, thereby reducing the measurement error caused by the increase in liquid density and ensuring the accurate measurement of the defect location by the guided wave sensor under any pressure environment below 8 MPa. Attached Figure Description

[0040] Figure 1 This is a cross-sectional structural diagram of a magnetostrictive guided wave sensor;

[0041] Figure 2 This is a schematic diagram of a pipeline non-destructive testing device.

[0042] Figure 3 hysteresis loop of Fe-Co material;

[0043] Figure 4 Magnetostriction coefficient of Fe-Co material under different magnetic field strengths;

[0044] Figure 5 A diagram showing the magnetic field strength generated by a permanent magnet on a magnetostrictive patch;

[0045] Figure 6 Comparison of detection signals between liquid-filled and non-liquid-filled pipelines;

[0046] Figure 7 Comparison of detection signals from a liquid-filled pipeline under different pressures; among them... Figure 7 a represents the defect detection signal of a liquid-filled pipeline using a permanent magnet sensor with a magnetic yoke under different pressures. Figure 7 b is a graph showing the variation of the amplitude of the detection signal wave packet under various pressures;

[0047] Among them, 1-Wall-shaped permanent magnet, 2-Detection coil, 3-Magnetorectal patch, 4-Magnetic yoke, 5-Pipe, 6-Hose clamp, 7-Elastic layer, 8-Sleeve;

[0048] 10-PC terminal, 11-Signal generator, 12-Power amplifier, 13-Voltage preamplifier, 14-Oscilloscope, 15-Pressure pump, 16-Excitation sensor, 17-Receiver sensor, 18-Pipe defect; Detailed Implementation

[0049] The invention will be further described in detail below with reference to the figures. This embodiment is only for specific illustration of the invention and should not be regarded as a limitation on the scope of protection.

[0050] The structure of the magnetostrictive guided wave sensor suitable for liquid-filled / high-pressure environments described in this invention is as follows: Figure 1 As shown, it includes: a tile-shaped permanent magnet 1, a detection coil 2, a magnetostrictive patch 3, a magnetic yoke 4, a hose clamp 6, an elastic layer 7, and a sleeve 8;

[0051] The positional relationship is as follows: On the outer side of the elastic layer 7, two arc-shaped magnetostrictive patches 3 are symmetrically pasted, with a spacing of 2-3 mm between the two patches 3, and the radial end of the patch 3 is the same length as the radial end of the elastic layer 7; a circular hose clamp 6 is respectively fitted on both ends of the outer side of the magnetostrictive patch 3, and a detection coil 2 is wound on the outer surface of the magnetostrictive patch 3 between the hose clamps 6 (Note that the hose clamp and the coil are on the same plane, and since the cross-sectional view shows both parts at the same time, the size of the hose clamp 6 is enlarged to show it in the gap). The elastic layer 7, the magnetostrictive patch 3 and the detection coil 2 form a hollow cylinder; a sleeve 8 is wrapped around the hollow cylinder, and a tile-shaped permanent magnet 1 is distributed in each of the four evenly distributed fan-shaped slots on the sleeve 8. A strip-shaped magnetic yoke 4 is fixed to each of the radial sides of each tile-shaped permanent magnet 1.

[0052] The term "radial" refers to the length direction of the pipe being inspected.

[0053] The elastic layer 7 is a closed or open cylindrical body. When it is an open cylindrical body, it has a radially oriented groove with a width of 0.5 to 1.0 cm. The material is polyurethane, and the sound velocity is 1520 m / s. -1 The attenuation constant is 0.05 dBcm. -1 The outer diameter is 42mm, the thickness is 1mm, and the radial length is 50mm. This makes it suitable for test pipes of different diameters. When the outer diameter of the test pipe is smaller than the diameter of the cylindrical inner core, the elastic layer 7 can be ensured to adhere to the test pipe wall by tightening the hose clamp 6. When the outer diameter of the test pipe is slightly larger than the diameter of the elastic layer, the inner diameter of the elastic layer 7 can be enlarged due to the through groove, so that the elastic layer 7 can still adhere to the test pipe wall.

[0054] The sleeve 8 is made of thermoplastic PLA. It has four fan-shaped slots inside for holding a tile-shaped permanent magnet with a yoke. The slots are separated by partitions. The sleeve's radial length is the same as the permanent magnet's. Its outer diameter is 60mm, inner diameter is 48mm, and radial length is 50mm. The sleeve wall thickness is 1mm. It can fix the position of the permanent magnet without interfering with the magnetic field. The sleeve can be a one-piece cylinder or two semi-circular cylinders connected by snap-fit.

[0055] The bottom layer is a polyurethane elastic layer, which reduces the acoustic impedance of sound waves transmitted through the medium and prevents the patch from corroding or undergoing destructive deformation. (This polyurethane acoustic material has the characteristics of good acoustic impedance matching with water and a low sound attenuation constant; sound velocity 1520 m / s) -1 Attenuation constant: 0.05 dB·cm -1 Magnetostrictive patches are symmetrically pasted around the elastic layer, and hose clamps are installed at both ends to apply prestress. A hollow cylindrical coil is inserted into the middle of the hose clamp, and four sets of tile-shaped permanent magnets are installed with triangular yokes. They are placed in the sleeve according to the rule that the polarity of adjacent ends is the same, and the sleeve is put on the outer layer of the hose clamp.

[0056] The aforementioned tile-shaped permanent magnet 1 is made of neodymium iron boron, serial number N45; outer diameter 56mm; inner diameter 50mm; radial length 50mm; center angle of each group of magnets is 70°; conductivity 7E+05S / m; remanence 835kA / m; coercivity 1.35T; the static magnetic field generated by the tile-shaped permanent magnet in the magnetostrictive patch is as follows: Figure 5 As shown, the circumferential magnetic field excited by the permanent magnet in the magnetostrictive patch is clockwise and counterclockwise, respectively. The maximum value of the magnetic field is 27.4 kA / m. The magnetic field distribution is relatively uniform, and the axial magnetic field around the two magnetostrictive patch interfaces is significantly weakened. The excited guided wave modes are relatively pure, with less longitudinal mode content, which is beneficial for the detection and identification of pipeline defect locations in the detection signal.

[0057] The detection coil 2 uses a wire with a diameter of 0.2mm (nominal wire diameter 0.2mm, nominal wire cross-sectional area 0.03142mm²). 2 The enameled wire (maximum outer diameter 0.239mm) is wound into a hollow cylinder. When used as an excitation sensor, it is wound with 100 turns, and when used as a receiving sensor, it is wound with 150 turns. The inner diameter of the finished cylindrical excitation coil is 0.65mm and the outer diameter is 1mm. The inner diameter of the cylindrical detection coil is 1mm and the outer diameter is 1.5mm. The hollow cylinder is fitted outside the magnetostrictive patch 3 and is located between the two end clamps 6 to provide an axial alternating magnetic field for the patch, exciting or receiving torsional wave signals.

[0058] The magnetostrictive patch 3 is rectangular in shape and located between the elastic layer 7 and the coil 2. It is made of an Fe-Co alloy with an alloy composition of 30% Fe and 70% Co. Its circumferential width along the pipe is 70 mm, its radial length is 50 mm (the patch, sleeve, elastic layer, and magnet all have a radial length of 50 mm), its thickness is 0.15 mm, and its relative permeability is 98 × 10⁻⁶. -6 Electrical conductivity 2.5E+06, density 8.57242 g / cm³ 3 The elastic modulus is 187.9 GPa, Poisson's ratio is 0.33, and the rigidity modulus is 70.698 GPa. Two rectangular patches are arranged symmetrically in a circle, leaving a 2-3 mm interface in the middle to facilitate the formation of a magnetic circuit with the permanent magnet. The magnetic properties of the magnetostrictive patch are as follows: Figure 3 , Figure 4 As shown, Figure 3 The hysteresis loop shown reflects the magnetization properties of ferromagnetic materials. The X-axis represents the magnetic field strength, with a measurement range of -400 to 400 kA / m, and the Y-axis represents the magnitude of the magnetic moment, which varies with the magnetic field strength from -200 A·m. 2 / kg increased to 200 A·M 2 / kg. As shown in the illustration, under low magnetic field strength, the slope of the hysteresis curve changes little, indicating insensitivity to changes in magnetic field strength. When the magnetic field of the ferromagnetic material changes little, the impact on signal variation can be reduced. Figure 4 The magnetostriction coefficient shown reflects the magnetostrictive ability of ferromagnetic materials. The X-axis represents the magnetic field strength, with a measurement range of -40 to 40 kA / m, and the Y-axis represents the magnetostriction coefficient, with the highest magnetostriction coefficient reaching 98 × 10⁻⁶. -6 PPM, with a saturated static magnetic field of 25kA / m, can achieve maximum magnetostriction. A high magnetostriction coefficient can improve the sensor's transduction efficiency and the excitation efficiency of the guided wave, increase the amplitude of the detection signal, and reduce or even eliminate the influence of high-pressure liquid filling pipeline on the signal amplitude attenuation.

[0059] The magnetostrictive patch is a known material, made by melting high-purity metal in a vacuum furnace under argon protection. The ingot is then hot-forged and rolled at high temperatures to form 8mm thick blocks. Through multiple heat treatments, the patch thickness is reduced from 8mm to 0.15mm. Finally, the alloy patch is annealed in a resistance furnace under nitrogen protection at 850°C.

[0060] The magnetic yoke 4 is made of silicon steel, with a radial strip shape and a right-angled triangular cross-section. The base of the yoke is 7mm long, the height is 3mm (the base is close to the coil 2, and the other right-angled side is attached to the side of the magnetic tile), and the radial length is 50mm, consistent with the patch and the permanent magnet. The relative permeability is 400, and the conductivity is 1818.182S / m. The magnetic yoke and the permanent magnet are coupled with epoxy resin to form a complete magnetic circuit. The magnetic yoke guides the magnetic field of the permanent magnet, enhancing the strength and uniformity of the circumferential magnetic field in the magnetostrictive patch 3.

[0061] The hose clamp 6 is made of 304 stainless steel and is installed at the edges of both ends of the magnetostrictive patch. It is resistant to 800℃ and has a resistivity of 0.73. It uses a threaded structure to apply prestress to the patch.

[0062] The installation method of the magnetostrictive guided wave sensor suitable for high-pressure / fluid-filled environments includes the following steps: wrapping the elastic layer around the pipeline, then pasting the magnetostrictive patch onto the elastic layer, fixing one hose clamp at each end of the patch, inserting a pre-wound hollow cylindrical coil (openable and closable) between the two hose clamps, applying stress through the hose clamps to make the patch and other components fit tightly, and finally putting the sleeve with permanent magnets on the outer layer of the hose clamps to complete the installation.

[0063] The above installation method is just one approach and is not limited to it. For example, depending on the actual application, it can also be installed by slipping it onto one end of the pipeline and then tightening it.

[0064] The aforementioned liquid-filled / high-pressure environment pipeline defect detection device, such as Figure 2 As shown, the system includes: a PC terminal 10, a signal generator 11, a power amplifier 12, a voltage preamplifier 13, an oscilloscope 14, a pressurization pump 15, an excitation sensor 16, and a receiving sensor 17. The connections are as follows: the PC terminal 10 is connected to the signal generator 11 and the oscilloscope 14; the signal generator 11 is connected to the detection coil of the excitation sensor 16 via the power amplifier 12; the oscilloscope 14 is connected to the detection coil of the receiving sensor 17 via the voltage preamplifier 13; the excitation sensor 16 and the receiving sensor 17 are respectively fitted onto the pipe to be tested.

[0065] The aforementioned method for detecting defects in pipelines in liquid-filled / high-pressure environments includes the following steps:

[0066] (9) Install excitation sensor 16 and receiving sensor 17 at one end of the pipeline respectively;

[0067] (10) Output the Hanning window modulated sinusoidal pulse waveform to the signal generator 11 via PC terminal 10;

[0068] (11) The signal generator 11 generates a pulse wave which is input to the power amplifier 12;

[0069] (12) The power amplifier 12 inputs the signal to the detection coil 2 of the excitation sensor 16;

[0070] (13) The voltage signal detected by the sensor 17 is input to the voltage preamplifier 13;

[0071] (14) The signal is amplified and filtered by voltage amplifier 13 and then input to oscilloscope 14;

[0072] (15) The signal is averaged 512 times by oscilloscope 14 and then input to PC terminal 10;

[0073] (16) After the PC performs wavelet transformation and other processing on the signal, the specific location of the defect on the pipeline is determined by the position of the wave packet in the detection signal and the propagation speed of the torsional wave.

[0074] In step (4), when the detection coil receives the pulse signal, it generates an axial alternating magnetic field, which interacts with the circumferential static magnetic field generated by the permanent magnet. According to the magnetostrictive effect, a torsional guided wave is generated in the magnetostrictive patch. The guided wave is transmitted from the patch to the pipe, and the guided wave propagates in the pipe liquid in the radial direction.

[0075] If there are no defects in the pipeline (defects can be pipeline corrosion pits, pipeline cracks, man-made welds, etc.), the received signal will not contain wave packets of corresponding defect reflection signals.

[0076] If a defect or end point is encountered during propagation and reflection occurs, the reflected signal, upon reaching the receiving sensor, alters the magnetization state of the magnetostrictive patch (i.e., generates a stress wave, which in turn causes deformation of the magnetostrictive patch, further changing its magnetization state). Based on the inverse magnetostrictive effect, the detection coil induces a voltage signal, which is then sent to the voltage preamplifier. The filling pipe receives the signal as follows: Figure 6 As shown in (c), the four wave packets from left to right represent the through signal, the left end echo, the defect echo, and the right end echo. The wave packet appearing at 0.98ms is the echo signal reflected back from the defect by the rightward-propagating guided wave. Based on the wave velocity of the torsional wave, the defect location can be calculated to be 1.3m to the right of the receiving sensor. The defect-free pipeline detection signal does not contain a wave packet at 0.98ms.

[0077] The PC terminal 10 mentioned above is specifically a Thinkpad T450s;

[0078] The signal generator 11 is specifically a Tektronix AFG2021;

[0079] The power amplifier 12 is specifically an Aigtek ATA-4014;

[0080] The voltage preamplifier 13 is specifically a Stanford SR560;

[0081] The oscilloscope 14 is specifically a Tektronix MDO4104C;

[0082] The PC terminal 10 is used for Matlab programming to generate a 5-cycle Hanning window modulated sinusoidal pulse wave. The designed waveform is input into the signal generator 11 with an excitation frequency of 45kHz and an output amplitude of 10V. The output signal is amplified tenfold by the power amplifier 12 to an amplitude of 100V and a current of 2.12A. The pulse signal is applied to the excitation sensor, which generates a torsional wave that propagates into the pipe. The pipe is a non-ferromagnetic 304 stainless steel pipe (it can be used with either ferromagnetic or non-ferromagnetic pipes without limitation, and the liquid in the pipe is also unrestricted; water was used in the experiment). The pipe is 2940mm long, 40mm in outer diameter, and 2mm thick. The excitation sensor 16 is located 34mm from the left end of the pipe, and the receiving sensor 17 is located 47mm from the right end of the excitation sensor. The defect 18 is located 2100mm from the left end of the pipe. When the torsional wave encounters a defect, it is reflected. When the reflected signal propagates to the receiving sensor, a voltage signal is induced due to the magnetostrictive inverse effect. The voltage signal is amplified and filtered by the voltage preamplifier 13. After being amplified 50 times, it is filtered with a bandwidth of 30kHz-100kHz. The signal is then input into the oscilloscope 14, where the average value is calculated 512 times to reduce the influence of noise. Finally, it is input to the PC for wavelet transform to further eliminate noise. The pressure pump 15 is installed at the right end of the pipeline and is connected to the semi-circular end cap by bolts. The pressure adjustment method is manual, which can keep the hydraulic pressure in the pipe constant. The pressure adjustment range is 0-8MPa.

[0083] Example 1: Under the same conditions, a traditional rectangular permanent magnet sensor and a designed tile-shaped permanent magnet sensor were used to detect non-fluid-filled pipes. Then, the designed tile-shaped permanent magnet sensor was used to detect both non-fluid-filled and fluid-filled pipes (at 0 MPa), and the results were compared. The main purpose of this example is to investigate whether the amplitude and signal-to-noise ratio of the detection signal by the designed tile-shaped permanent magnet sensor are improved compared to the traditional rectangular permanent magnet sensor, and to verify the changes in the detection signal received by the designed tile-shaped permanent magnet sensor when detecting non-fluid-filled and fluid-filled pipes.

[0084] Experimental platform setup: First, connect the PC, signal generator, power amplifier, voltage preamplifier, oscilloscope, and pressurization pump in sequence; install the excitation sensor 34mm from the left end of the pipe and connect it to the power amplifier; install the receiving sensor 47mm from the right end of the excitation sensor and connect it to the voltage preamplifier; the defect in the experiment is an artificially created rectangular crack with a length (pipe radial direction) of 2mm, a width (pipe circumferential direction) of 20mm, and a depth (pipe thickness direction) of 2mm, located 2100mm from the left end of the pipe, and is detected at room temperature.

[0085] Experimental Procedure and Results: An amplified pulse signal is applied to both ends of the excitation sensor's detection coil. This interacts with the static magnetic field generated by the permanent magnet, producing a torsional wave in the magnetostrictive patch. The torsional wave propagates through the elastic layer into the tested pipe. Within the pipe, the torsional wave propagates along the pipe wall towards both ends, reflecting upon encountering the ends or defects. The reflected torsional wave then propagates to the receiving sensor, inducing a voltage signal. After amplification, filtering, and averaging, the detection signal is as follows: Figure 6 As shown in the figure, Figure 6 (a) Signal for detecting defects in non-fluid-filled pipes using a rectangular permanent magnet patch sensor. Figure 6 (b) To detect defect signals in non-fluid-filled pipelines using a permanent magnet sensor with a yoke. Figure 6 (c) For detecting defects in liquid-filled pipelines using a permanent magnet sensor with a yoke, such as... Figure 6 As shown in (a), the echo packets measured from left to right are: through signal, left echo, defect echo, and right echo. The echo packet appearing at 0.98 ms is the echo signal reflected back from the defect by the rightward-propagating guided wave. The defect-reflected signal travels a distance of 3.07 m from the excitation sensor to the receiving sensor. According to the formula... The group velocity of the guided wave can be calculated to be 3070 m / s, which is consistent with the group velocity of the T(0,1) mode signal. Therefore, the wave packet appearing at 0.98 ms is a defect reflection signal in the T(0,1) mode. In non-fluid-filled pipelines, a rectangular permanent magnet sensor is used for detection. The detected voltage signal amplitude is small, the echo wave packet is wide, and the maximum amplitude is 53.76 mV, making it difficult to pinpoint the precise location of pipeline defects. Figure 6 As shown in (b), when using a tile-shaped permanent magnet sensor to detect a non-fluid-filled pipeline, the detected voltage signal amplitude is higher, the echo packet is narrower, and the maximum amplitude is 136.51mV, which is twice as high as the signal detected by a rectangular permanent magnet sensor. Furthermore, the detected signal has weaker content of other modes and a higher signal-to-noise ratio. Figure 6(c) shows the detection results of the tile-shaped permanent magnet sensor on the liquid-filled pipeline. The maximum amplitude of the detection signal for the liquid-filled pipeline is 92.53mV, which is smaller than the amplitude of the detection signal for the non-liquid-filled pipeline. The attenuation of the T(0,1) guided wave is due to the influence of liquid viscosity on shear force. Liquid viscosity has virtually no effect on the group velocity of the guided wave, but the amplitude of the guided wave decreases with increasing viscosity. The rigid boundary between the stainless steel pipeline and the water column generates interference signals of other modes. The end caps installed at both ends of the pipeline increase the wave packet width of the echo signal. Experimental results show that in a liquid-filled environment, the tile-shaped permanent magnet sensor can excite the T(0,1) mode guided wave and can correctly detect the location of pipeline defects.

[0086] Example 2: Using the designed tile-shaped permanent magnet sensor, the pipeline was tested in a liquid-filled environment of 0-8MPa to verify the accuracy of the guided wave sensor in measuring pipeline defects and the changes in the detection signal under different pressures.

[0087] Experimental platform setup: First, connect the PC, signal generator, power amplifier, voltage preamplifier, oscilloscope, and pressure pump in sequence; install the excitation sensor 34mm from the left end of the pipe and connect it to the power amplifier; install the receiving sensor 47mm from the right end of the excitation sensor and connect it to the voltage preamplifier; connect the pressure pump to the right end of the pipe and use the pressure pump to control the pressure inside the pipe, keeping the pressure between 0-8MPa.

[0088] Experimental Procedure and Results: An amplified pulse signal was applied to both ends of the excitation sensor's detection coil. Interacting with the static magnetic field generated by the permanent magnet, a torsional wave was generated in the magnetostrictive patch. This torsional wave propagated through the elastic layer into the tested pipe. Within the pipe, the torsional wave propagated along the pipe wall towards both ends, reflecting upon encountering the ends or defects. The reflected torsional wave then propagated to the receiving sensor, inducing a voltage signal. After amplification, filtering, and averaging, the result is as follows: Figure 7 As shown, Figure 7 (a) shows the test results of the filling pipeline under different pressures (0, 2, 4, 8 MPa). From left to right, the echo packets are the through signal, left echo, defect echo, and right echo, respectively. Figure 7(b) The amplitude of each echo packet varies with pressure. As shown in the figure, the signal amplitude attenuation increases with increasing pressure. The left echo in the detected signal has the largest attenuation amplitude at 8 MPa (approximately 0.89 times), while the amplitudes of the defect echo and the right echo are smaller and do not change significantly with increasing pressure. The attenuation of the guided wave is mainly affected by liquid viscosity and liquid pressure. Increased liquid pressure leads to increased liquid density. Liquid density has little effect on the group velocity of the T(0,1) mode guided wave, but it has a significant impact on the signal attenuation amplitude. When the liquid density is low, the signal amplitude decreases rapidly with increasing density, while when the density is high, the signal amplitude decreases slowly with increasing density. At lower frequencies, liquid viscosity and density are proportional to the square of the amplitude attenuation. Experiments have shown that the proposed tile-shaped permanent magnet magnetostrictive patch sensor can accurately detect the location of defects in liquid-filled pipes under different pressures and improve the amplitude and signal-to-noise ratio of the guided wave signal.

[0089] As can be seen from the above embodiments, the present invention addresses the problem that changes in the liquid density of Fe-Co magnetostrictive materials in high-pressure liquid-filled pipelines can lead to a decrease in sensor measurement accuracy, and improves the sensor structure.

[0090] 1. Traditional rectangular magnetized permanent magnets generate weak and uneven magnetic fields, resulting in complex guided wave modes and low received signal amplitude. The viscosity and density of the pipe liquid cause attenuation of the guided wave signal amplitude, making it difficult to pinpoint the exact location of defects. This patent proposes a design where tile-shaped permanent magnets are arranged in a circular pattern around the pipe with identical polarities at both ends, and a triangular yoke is installed around them. The yoke guides the magnetic field generated by the permanent magnets into a magnetostrictive patch, enhancing the magnetic field strength. By adjusting the size and lift-off distance, the optimal bias magnetic field of the magnetostrictive material is maintained, ensuring the sensor's measurement accuracy in high-pressure liquid-filled pipes. This patent proposes a sensor structure design suitable for high-pressure liquid-filled environments. A hose clamp provides prestress to the sensor, and a polyurethane elastic layer reduces the acoustic impedance at the medium interface, achieving unidirectional excitation of the guided wave and enhancing its transmission efficiency. By maintaining the optimal magnetic field strength and uniformity of the ferromagnetic material, the optimal excitation efficiency and signal-to-noise ratio of the torsional guided wave are maintained, eliminating the influence of the liquid viscosity and density in the liquid-filled pipe on the accuracy of the detection signal.

[0091] 2. To ensure constant pressure measurement during high-pressure pipeline operation, semi-circular end caps were installed at both ends of the pipeline. These end caps are strictly sealed and have external threads. A pressure pump was installed at one end of each end cap to control pressure changes within the pipeline. Comparative experiments were conducted on the various components of the sensor to determine the optimal dimensions of each material. The magnetostrictive patch was formed into two semi-circles and coupled around the pipeline, with a 2-3mm notch at the interface between the two patches to form a complete magnetic circuit with the permanent magnet. The radial length of the magnetostrictive patch is 50mm. Combined with a Hanning window modulated sinusoidal pulse with a center frequency of 45kHz, a high signal amplitude can be obtained.

[0092] The software or protocols involved in this invention are all known technologies.

[0093] Based on the above improvements, and after extensive experiments and optimization of the configuration of each part, a magnetostrictive guided wave sensor for high-pressure liquid filling environment was designed. This sensor can excite and detect torsional wave signals and optimize the detection signal.

[0094] Matters not covered in this invention are common knowledge.

Claims

1. A magnetostrictive guided wave sensor suitable for high-pressure / liquid-filled environments, characterized in that... The sensor includes a tile-shaped permanent magnet, a detection coil, a magnetostrictive patch, a magnetic yoke, a hose clamp, an elastic layer, and a sleeve. The positional relationship is as follows: the elastic layer is wrapped around the pipeline, and two arc-shaped magnetostrictive patches are symmetrically pasted on the outside of the elastic layer. The distance between the two patches is 2-3 mm, and the radial end of the patch is the same length as the radial end of the elastic layer. A circular hose clamp is fitted at the edge of each end of the magnetostrictive patch. A detection coil is wound on the outer surface of the magnetostrictive patch between the hose clamps. The elastic layer, the magnetostrictive patch and the detection coil form a hollow cylinder. The hollow cylinder is covered by a sleeve. In each of the four evenly distributed fan-shaped slots on the sleeve, there is a tile-shaped permanent magnet. On each radial side of each tile-shaped permanent magnet, a strip-shaped magnetic yoke is fixed. The elastic layer is a closed or open cylindrical body; when it is an open cylindrical body, a through groove with a width of 0.5 to 1.0 cm is opened radially; the material is polyurethane. The sleeve is made of thermoplastic plastic, and has four sector-shaped grooves inside. The radial length of the sleeve is the same as that of the permanent magnet. The aforementioned tile-shaped permanent magnet is made of neodymium iron boron. The detection coil is a hollow cylinder wound with enameled wire, with 50 to 200 turns; The magnetostrictive patch is rectangular in shape, located between the elastic layer and the coil, and is made of Fe-Co alloy. The magnetic yoke is made of silicon steel, has a radial strip shape, a right-angled triangular cross-section, a height less than or equal to the thickness of the magnetic tile, and a radial length the same as that of the patch and the permanent magnet. The hose clamp is made of stainless steel.

2. A defect detection device for pipelines in liquid-filled / high-pressure environments, characterized in that: The device includes: a PC, a signal generator, a power amplifier, a voltage preamplifier, an oscilloscope, a pressure pump, an excitation sensor, and a receiving sensor; the connection relationship is as follows: the PC is connected to the signal generator and the oscilloscope respectively; the signal generator is connected to the excitation sensor through the power amplifier; the oscilloscope is connected to the receiving sensor through the voltage preamplifier; the excitation sensor and the receiving sensor are respectively fitted onto the pipeline to be tested; The excitation sensor and the receiving sensor have the same structure, both being the magnetostrictive guided wave sensor as described in claim 1, wherein the number of turns of the detection coil in the receiving sensor is greater than or equal to the number of turns of the detection coil in the excitation sensor.

3. A method for detecting defects in pipelines in liquid-filled / high-pressure environments, based on the pipeline defect detection device for liquid-filled / high-pressure environments as described in claim 2, characterized in that... Includes the following steps: (1) Install the excitation sensor and the receiving sensor at one end of the pipeline respectively; (2) Output the Hanning window modulated sine pulse waveform to the signal generator via the PC terminal; (3) The signal generator produces a pulse wave which is input into the power amplifier; (4) The power amplifier inputs the signal to the detection coil of the excitation sensor; When the detection coil receives a pulse signal, it generates an axial alternating magnetic field, which interacts with the circumferential static magnetic field generated by the permanent magnet. According to the magnetostrictive effect, a torsional guided wave is generated in the magnetostrictive patch. The guided wave is transmitted from the patch to the pipe and propagates radially in the pipe wall and liquid. If there are no defects inside the pipe, the received signal will not contain wave packets of the corresponding defect reflection signal; If a defect or end is encountered during propagation and a reflection occurs, the reflected signal will change the magnetization state of the magnetostrictive patch when it reaches the receiving sensor, causing the detection coil to generate a voltage signal, and then proceed to the next step. (5) The voltage signal detected by the detection coil of the receiving sensor is input to the voltage preamplifier; (6) The signal is amplified and filtered by a voltage amplifier before being input to the oscilloscope; (7) The signal is averaged by an oscilloscope and then input to the PC. (8) After the PC performs wavelet transformation processing on the signal, the specific location of the pipeline defect is finally determined by the position of the defect echo in the detection signal and the propagation speed of the torsional wave.

4. The method for detecting defects in pipelines in liquid-filled / high-pressure environments as described in claim 3, characterized in that the defects are pipeline corrosion pits, pipeline cracks, or weld seams.

5. The method for detecting defects in a liquid-filled / high-pressure environment pipeline as described in claim 3, characterized in that the pressure environment of the pipeline is 0-8 MPa.

6. The method for detecting defects in pipelines in liquid-filled / high-pressure environments as described in claim 3, characterized in that: The liquid is water, glycerin, or petroleum.

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